Stabilizer for organic compounds

ABSTRACT

COMPOUNDS OF THE FORMULA   2-R1,4-(R4O-CO-CH(-R3)-CH2-),6-R2-PHENOL   ARE PREPARED BY REACTING A MANNICH BASE   2-R1,4-(N(-R)2-CH2-),6-R2-PHENOL   WITH A CARBOXYLIC ACID ESTER OF THE FORMULA   R3-CH2-CO-OR4   AND ARE STABILIZERS FOR ORGANIC MATERIALS AGAINST DETERIORATION BY OXYGEN, LIGHT AND HAAT. IN THE FORMULAE, R1 AND R2 IS ALKYL, R3 IS -CN OR -COOR4, AND R4 IS AN ALKYL, ARALKYL, CYCLOALKYL, ETHER OR THIOETHER GROUP.

United States Patent 1m. (:1. C0 7c 69/76 US. Cl. 260-473 S 4 Claims ABSTRACT OF THE DISCLOSURE Compounds of the formula noQcm-cn-ooon,

are prepared by reacting a Mannich base HOQCHIIKR):

with a carboxylic acid ester of the formula and are stabilizers for organic materials against deterioration by oxygen, light and heat.

In the formulae, R and R is alkyl, R, is CN or COOR and R is an alkyl, aralkyl, cycloalkyl, ether or thioether group.

This is a continuation of application Ser. No. 661,191, filed Aug. 17, 1967, now abandoned.

This invention relates to novel stabilizers and a method for their preparation.

Said stabilizers have the formula R1 no cm-onoo OR;

I R: R: (I)

In said formula R and R are the same or different, linear or branched alkyl groups of which at least one contains 1 to 6 carbon atoms and preferably at least one is linked with a tertiary C-atom to the aromatic nucleus R is CN or -COOR and R is a linear, branched, cyclic or aryl substituted alkyl,

3,830,828 Patented Aug. 20, 1974 thioether, or ether group containing a total of 12() carbon atoms.

These compounds can be prepared in a simple manner in excellent yields by reacting a Mannich base of the general formula wherein R and R are as above and R is alkyl, preferably a lower alkyl, with a carboxylic acid ester of the general formula wherein R and R are as above. The reaction is carried out in the presence of a catalytic amount of an alkali metal base or an alkaline earth metal base, preferably an alkali or alkaline earth metal alcoholate, in an anhydrous inert organic solvent.

The preparation of Mannich bases from phenols, formaldehyde, and secondary amines is known.

Suitable solvents are hydrocarbons, glycol ethers and other high boiling ethers. Also alcohols R OH can be used. We prefer to employ aromatic hydrocarbons.

A preferred mode of operation consists in refluxing one mole of the Mannich base with one mole of the carboxylic acid ester (malonic acid ester, cyanoacetic acid ester) in the presence of 1 to 20 g. of alkali or alkaline earth metal alcoholate in about 1 liter of toluene, preferably in a nitrogen atmosphere, for 2 to 3 hours. After cooling, the catalyst is removed, e.g. by neutralization with diluted acid and extraction with water, the reaction mixture is dried, the solvent is distilled off, and the residue is purified, e.g., by recrystallization. The yield is about 70 to 90 percent of the theory.

The smooth course of reaction could not be expected because it was known, e.g., from the book by H. Hellmann and G. Opitz on alpha-Aminoalkylation (publ. by Verlag Chemie, Germany), p. 284, that phenol-Mannich bases can be C-alkylated, e.g., with malonic acid esters, only when the ammonium salts of the phenol bases are used as starting material, whereby said ammonium salts are diflicult to prepare.

The following examples for the preparation of the compounds (I), and for their use as stabilizer, are given for their sake of illustration and without intention of limiting the invention to the specific details disclosed:

EXAMPLE 1 Preparation of (4-hydroxy-3-methyl-5-tert. butyl benzyl) malonic acid distearyl ester (Stabilizer II) 22.1 g. (0.1 mole) of (3-methyl-5-tert. butyl-4- hydroxybenzyl)dimethylamine were refluxed with 60.9 g. (0.1 mole) of malonic acid distearyl ester and l g. of magnesium ethylate in cc. of toluene for 3 hours under nitrogen. The solution was then cooled and filtered from the magnesium ethylate; subsequently, the toluene was distilled off in vacuo, and the residue was recrystallized from acetone. There were obtained 71 g. of (4-hydroxy-3- methyl-S-tert. butyl benzyl) malonic acid distearyl ester in a yield of percent of theory. M=69-71 C.

In an analogous manner, the compounds listed in the following Table I were obtained. The substituents R R R and R refer to formula (I). The structure was determined on the basis of the IR spectra and by quantitative analysis.

TABLE I Melting point Yield Stabilizer No. R; R7 R R4 0.) (percent) -CH tert.Butyl CN C2H 180-182 67 CHa-.. -.do 'COOR4 CH3 191-103 72 CH do COOR4 -CHz(3HC4Ho Liquid 84- CzH5 CH3 -410 000R; Liquid P 69 CH: .do 000B; Liquid 73 CH; do COOR4 CH2CHzOC4Ho 6062 '75- T --CH: dn COOR4 -C 21 4042 '92; IT -("H'-r fin COOR4 -Cu; 37 69-71 .94 III tert.Butyl do COORr -CH2CH2SC10H33 37-40 70 r do do COOR -C1sHa7 65-68 89 V Isopropyl Isopropyl COOR4 -C1sHs1 68-70 80 The compounds of formula I are good antioxidants and light and heat stabilizers for organic compounds, particularly for polymeric compounds such as polyolefins, polyamides, shock-resistant polystyrene-containing butadiene-styrene polymers, ABS polymers (copolymers of acrylonitrile, butadiene, and styrene), vegetable and animal oils and fats, plasticizers such as phthalates, and mineral oils.

Particularly good stabilizers are those of the formula HO CHr- (EH-41 DORA,

a CH I --CH;

CH: (IV) in which R, has the significance given above and contains a total of 4-20 C atoms.

Generally, we prefer esters of higher alcohols, particularly those which contain sulfur in ether linkage. Such esters are compatible with polymeric resins, fats and mineral oils and exert, due to their low volatility, a good stabilizing effect on these materials even after prolonged thermal stresses.

Generally, the stabilizers are used in an amount of 0.01 to 10 percent, calculated on the total weight of the material to be stabilized.

As the following examples, particularly example 5, show, our novel stabilizers have an improved stabilizing effect when compared with known purely organic stabilizers such as the mixtures of alkylated phenols (German DAS 1,035,137) thiobisphenols, and w-(hydroXy-alkylphenyl)-alkane carboxylic acid esters (German DAS 1,201,349). In contrast to the experience stated in the with'alkali metal (e.g.sodium) derivatives of carboxylic acid esters of the formula i or by reacting 2,6-alkylatedphenols 'with' halogenated carboxylic acid esters of the formula Hal- 011 90011!" Both methods are inferior to the above described preparation starting from the readily'available Mannich bases and carboxylic acid esters because the starting compounds of formulae V and VII are more difiicultly' available.

The following examples illustrate compounds as stabilizers.

EXAMPLE 2 I Stabilization of polypropylene Two unstabilized polypropylene powders of melting index 1.6 of different origin (called A and B in Table II) were used. To parts by weight of said powders, the stabilizers listed in Table II were added. 'All' mixtures were treated for 10 minutes at 180 C. on a laboratory roll mill, and the obtained films were pressed at 200 atm. and at a temperature of 210 C. From the obtained 1 mm. thick sheets, 5 strips, were cut out and subjected by storage in a drying cabinet at C. to an accelerated ageing; the time was determined after which an oxidative decomposition could be observed by the brittle test.

Stabilizer L =4,4-thiobis- (6-tert.butyl-m-cresol) tStabilizer M=fl-(3,5-di-tert.-butyl-4-hydroxy-phenyl)-propion.ic acid s eara e.

DLTDP=dilaurylthiodipropionate; Stabilizer II and III, see Table I. "1

The results illustrate the superior effect of the stabilizers of the invention.

EXAMPLE 3 Stabilization of an ABS resin (40% styrene,

40% acrylonitrile, butadiene) I Mixtures of 100 parts by weight of-ABSwith astabilizer and 2 parts of 1,Z-bis-stearoyl-aminoethane as lubricant were rolled on a laboratory roller. mill f0rw10-.min'utes at C., and the obtained films were pressed at a pressure of 200 atm. at a temperature of C. to sheets of 1 mm. thickness. Test specimens. cut from said sheets were stored in a drying cabinet at 110 C. to produce accelerating ageing, and the effect of the-stabilizers was determined by the discoloration and brittleness of the specimens. The results are given in Table III.

TABLE III Time in dry 'ing ca'binet before 5- r 'j-'." I becoming Test H H .Color after -,,;brittle No. Stabrhzer (parts by weight) "10 days (days) 1 0.5 2,6di-tert.bntyl phenol," Light yello 37 0.25 2,6-dimethylphenolr! f '31 2. 0.5 stabilizer L 42 .5 stabihzer I (Table I the use of the novel- As the Table III shows, the stabilizers I and II of the invention exceed the stabilizing efliciency of the known stabilizers.

EXAMPLE 4 Stabilization of polyamides (condensation products of dicarboxylic acid and diamines) 100 parts by weight of polyamide (nylon 6.6) each were mixed with the stabilizers listed in Table IV and extruded at 250 C. to sheets from which samples were cut and subjected to accelerated ageing in a drying cabinet at 140 C.

The stabilizing effect was determined by the brittleness of the samples. As will be seen from Table IV, the stabilizers of the invention exceed the effect of prior art antioxidants. Addition of phosphite improves considerably the early color of the extruded sheets.

Stabilization of mineral oil In tests -l4,100 g each of a mineral oil were mixed with the stabilizers listed in Table V, and 5 liters of oxygen were passed through the liquids for 90 minutes at 190 C. The produced decomposition was determined by the increased discoloration, measured by the Gardner color values, and by the increased viscosity. The mineral oil itself at the start of the tests had a Gardner color value of 3-4, and at 20 C. a viscosity of 144 cps.

TABLE V Viscosity Test Gard- (cps.) at No. Stabilizer (g.) ner 20 C.

10. 0.1 stabilizer L (Table II) 14 165 11-.. 0.1 stabilizer M (Table II)- 9 192 12- 0.1 stabilizer I (Table I) 7 180 13 0.5 stabilizer I (Table I), 0.05 trinonylphenyl phosphite 9 165 14 0.05 2,4,6-tert.butyl phenol, 0.05 2,4

dimethylphenol 12 188 6 The table shows the good results obtained with the novel stabilizer, particularly when used together with a phosphite.

EXAMPLE 6 Stabilization of vegetable oils and plasticizers The same stabilizers as employed in Table V were used in a similar manner for a vegetable oil (olive oil) and a plasticizer (dioctylphthalate). The results were similar to those obtained with the mineral oil.

What is claimed is:

1. A new compound corresponding to the formula wherein R is selected from the group consisting of stearyl and sulfur interrupted alkyl and oxygen interrupted alkyl having up to 20 carbons.

2. The compound of claim 1 wherein R is sulfur interrupted alkyl.

3. The compound of claim 1 wherein R is oxygen interrupted alkyl.

4. The compound of claim 1 wherein R is stearyl.

References Cited UNITED STATES PATENTS 3,721,704 3/1973 Dexter "260-473 S 3,247,240 4/1966 Meier et a1. 260-473 3,029,276 4/ 1962 Hausweiler et al "260-47 3 3,247,240 4/ 1966 Meier et a1. 260473 FOREIGN PATENTS 11,030 8/1960 Japan 260521 11,030 8/1960 Japan 260521 OTHER REFERENCES Adams et 21., Organic Reactions, VII, pp. 102, 103, 126, 127 (1963).

LOR-RAINE A. WEINBERGER, Primary Examiner US. Cl. XiR.

99163; 25256 R; 26045.85; 465 D, 475 B 

